Nerve Tingles

Understanding the Tingles of "Pins and Needles"

A restriction in blood flow, whether through pressure, temperature, or other means, is called ischemia, and while it can create serious problems depending on cause and duration it can also create a great deal of discomfort when it is relieved. The feeling that can follow ischemia is often described as, "a disagreeable tingling or pricking sensation" when impulses in the nervous system once again transmit. This sensory phenomenon is referred to as paraesthesia, and this tingling or prickly sensation that is experienced is the result of the changes in excitability that ischemia causes in the nerve cells of the affected region. When there is pressure placed on a nerve, the nerve is unable to receive any oxygen from the bloodstream due to the lack of new blood flow to the axon of the nerve. This also causes the nerve to be unable to get rid of wastes such as carbon dioxide and lactic acid and to attain glucose vital to the nerves functioning. All of these factors make it difficult if not impossible for the nerve cells in the region to become excitable and transmit messages. Once the pressure on the nerve is released and blood flow rises to a normal rate the nerve then enters a superexcitable state, which causes increased sensory awareness of a specific body region.

It is only after the buildup of chemical and electrical energy in the nerve cell is able to be released that the tingling or prickly feeling sets in. Ischemia creates this buildup through the reduction or elimination of blood supply, and that is why it is the relief of ischemia that actually causes the paraesthesia. While the feeling certainly isn't a pleasant one, the ability to feel it is a good sign, and it's also nice to know that your body is getting the blood it needs.

References

Kugelberg, E. (1948). Activation of human nerves by ischemia. Archives of Neural Psychiatry 60(2): 140-52.